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Eastern redbud (Cercis canadensis) is a small, short-lived
deciduous tree found throughout the eastern United States. Redbud
is also known as Judas-tree. According to legend, Judas Iscariot
hanged himself from a branch of the European species Cercis
siliquastrum (13). Eastern redbud is a strikingly conspicuous
tree in the spring because it flowers before other tree leaves
form. The wood is heavy, hard, and close-grained, but because of
the small size and irregular shape of the tree it is of no
commercial value as a source of lumber. This tree is most valued
as an ornamental and is extensively planted.

Habitat

Native Range

The range of eastern redbud is from New Jersey and southern
Pennsylvania northwest to southern Michigan, southwest into
southeastern Nebraska, south to central Texas, and east to
central Florida (8). A disjunct population of redbud extends from
the Trans-Pecos and south Texas into Mexico.

-The native rane of eastern redbub.

Climate

A wide range of climatic conditions are present in the large
geographical range of redbud. Mean annual precipitation is less
than 510 mm (20 in) in dry south Texas and approximately 1270 mm
(50 in) in moist central Florida. Mean annual snowfall in the
northern perimeter of redbud is about 90 cm (35 in). Mean January
temperatures vary from -8° C (18° F) to 16° C (61°
F) within the native range of redbud. Mean July temperatures vary
from about 21° C (70° F) in southern Pennsylvania to 26°
C (79° F) in central Florida. Frost-free days can vary from
160 to 300 days.

Soils and Topography

Redbud is found on a variety of sites ranging from xeric to mesic
but grows better on moist, well-drained sites. It is normally
more abundant on south-facing slopes where sunlight is more
intense and there is less plant competition (11). This species
does not usually grow on flooded sites because it cannot endure
inundation or survive in poorly aerated soils.

The tree grows well in a variety of soil textures but is not found
in coarse sands (11). It requires some fine or colloidal
material. Redbud is tolerant of a wide pH range but grows best
where the pH is above 7.5. It is prevalent on limestone outcrops
and on alkaline soils derived from them (11,12). Redbud is
tolerant of nutrient deficiencies. Therefore, less competition
can occur from associated trees that are less vigorous on the
nutrient deficient sites. In Indiana no relationship was noted
between distribution of redbud and soil calcium or magnesium.
Redbud is found on soils of most soil orders, but most commonly
on those of the orders Alfisols and Mollisols.

Associated Forest Cover

Redbud is a regular but usually not a common understory component
of many forest types throughout the Eastern United States. It is
not a commercial timber species, and although it grows in many
forest cover types, it is not listed in all of them by the
Society of American Foresters (4).

Life History

Reproduction and Early Growth

Flowering and Fruiting- Redbud flowers are pink to reddish
purple, and rarely white. They are home on pedicels in clusters
of two to eight. Flowers are produced from small buds on old
twigs, branches, and trunks. Flowers are bisexual and the tree is
self-pollinating. Flowering usually occurs sometime from March to
May and precedes leafing. In Indiana, the tree requires 30 days
of temperatures averaging more than 10° C (50° F) .
Previous winter chilling also enhances flowering (11).
Pollination is usually accomplished by bees. After 2 or 3 weeks
leaves appear and the flowers drop. The ovaries of one to several
flowers in most flower clusters enlarge and develop into fruits
that reach their full size by midsummer (13). Fruits are flat
reddish-brown pods about 1.3 cm (0.5 in) wide and 5 to 10 cm (2
to 4 in) long (16). Each fruit contains 4 to 10 brown, hard,
compressed bean-like seeds, each about 6mm (0.25 in) long. The
fruits remain on the tree until after leaf fall; some persist
throughout winter (15).

Seed Production and Dissemination- Seeds are released by
the opening of fruit sutures or decay of the fruit wall. Most
seeds are dispersed during fall and winter by wind and animals.
Many seeds are injured by insects. Those that fall to the ground
usually remain dormant for several years (1).

For artificial propagation, seeds should be collected, cleaned,
and dried when ripe to avoid insect damage. Dried seeds can be
stored in sealed glass or metal containers at 2' to 5' C (35' to
41° F). Seed treatment is necessary for propagation because
redbud shows delayed germination due to impermeability of the
seed coat to water and dormancy of the embryo (1). The seed coat
can be made permeable to water by mechanical scarification or by
immersion in boiling water or in concentrated sulfuric acid for
about 30 minutes. After scarifying, seeds should be stratified in
moist sand at about 5° C (41' F) for 5 to 8 weeks (14).

Prepared seeds should be sown in well-prepared seedbeds in late
April or early May (14). Moist soil should cover seeds at a
maximum depth of 0.5 em (0.2 in). Propagation can also be
accomplished by layering or cuttings.

Sapling and Pole Stages to Maturity

Growth and Yield- Development of young redbud to the
flowering stage is rapid. Young redbuds have been observed first
flowering when less than 7 years old but do not fruit the first
year of blossoming. Annual cambial growth begins just before
flowering and shoot growth usually begins during flowering (11).
In Indiana terminal growth of saplings started when the weekly
mean of the daily mean temperature reached 13° C (55°
F). Maximum growth was reached the fourth week and growth ceased
after 6 to 10 weeks under low soil moisture conditions. With
adequate soil moisture, terminal growth continued until frost.
More than 1076 lux (100 lumens/ft²) of light and more than
13 hours of daylight daily are needed to maintain terminal growth
of saplings.

Rooting Habit- Redbud develops a deep taproot that
descends rapidly the first few years if the soil permits. Initial
growth depends on soil moisture and the absence of a tight clay
subsoil. If impenetrable subsoils are present the taproot grows
horizontally. Secondary roots appear when the taproot is 5 to 8
cm (2 to 3 in) long and grow rapidly.

Reaction to Competition- As redbuds grow and mature they
become less shade tolerant. Old trees usually suffer from heart
rot and cannot normally tolerate severe competition and shade.
Redbud is most accurately classed as tolerant of shade.

Damaging Agents- Redbud is a host to a variety of insects,
but damage is not normally severe. Bark and phloem borers include
three species of Hypothenemus, and Pityophthorus
lautus (2). A seed beetle, Gibbobruchus mimus, breeds
in the seed of redbud.

Numerous wood borers have been found in redbud. Agrilus
otiosus, three species of Hypothenemus, three species
of Micracis, two species of Microcisella,
Pityophthorus lautus, Ptosima gibbicollis, and Thysanoes
fimbricornis all inhabit portions of the wood of redbud.

Other insects feed on the leaves of redbud. The redbud leaffolder,
Fascista cercerisella, feeds on leaves which the larvae
web together. The grape leaffolder, Desmia funeralis, an
important pest of grape, also feeds on redbud. The Japanese
weevil, Callirhopalus bifasciatus, and Norape ovina
both consume redbud leaves.

Other insects feed on redbud by extracting juices from the plant.
The twolined spittlebug, Prosapia bicincta, has been
recorded feeding on redbud. The terrapin scale, Mesolecanium
nigrofasciatum, and San Jose scale, Quadraspidiotus
perniciosus, like most of the other redbud parasites, inhabit
a variety of hosts including redbud. The periodical cicada, Magicicada
septendecim, lays its eggs in more than 70 species of trees
and other plants, including redbud.

There are three main diseases of redbud: leaf anthracnose, Mycosphaerella
cercidicola, Botryosphaeria canker, and Verticillium wilt
(6). The most serious is the canker Botryosphaeria ribis or
its variety chromogena. The species is mainly a saprobe;
the variety is a parasite. This variety produces stem and twig
lesions and entire groves of redbuds have been killed by this
disease. Verticillium wilt (Verticillium albo-atrum) sometimes
kills redbuds, especially in the Midwestern United States. Redbud
is vulnerable to Texas root rot (Phymatotrichum omnivorum),
but redbud is not commonly grown in its range. A variety of
sap and heart rots also infect eastern redbud.

Special Uses

The eastern redbud is extensively planted as an ornamental
throughout the Eastern United States. It is tolerant of a wide
range of site conditions, is not especially vulnerable to insects
or diseases, is relatively easy to maintain, and makes a
beautiful shrub or small tree, especially when flowering.

Bark of redbud has been used as an astringent in the treatment of
dysentery. Flowers of the tree can be put into salads or fried
and eaten (16). There is some documented wildlife use of redbud
fruit. Cardinals have been observed feeding on the seeds, and
seeds have been consumed by ring-necked pheasants rose-breasted
grosbeaks (5), and bobwhites (7) White-tailed deer and gray
squirrels have also been observed feeding on the seeds (5).
Flowers of the tree are regarded as important in the production
of honey by bees (10).

Genetics

Donselman (3) investigated morphological variation in
trees grown from seed collected from 13 diverse locations in the
range of redbud. He concluded that trees from more xeric
locations in the Southwestern and western portions of the range
exhibited adaptations to high solar radiation, drying winds, low
humidity, low soil moisture, and other environmental factors
associated with high evapotranspiration. Leaves from those plants
were thicker and smaller, had increased pubescence, and showed
more efficient stomatal geometry than trees from mesic locations.

Two subspecies of redbud have been identified: Texas redbud (Cercis
canadensis var. texensis) found in southern Oklahoma,
Trans-Pecos Texas, and southeastern New Mexico; and eastern
redbud (C. canadensis var. canadensis) found in
the remainder of the range of redbud (9). Another native Cercis
species, California redbud (C. occidentalis), is
found in Utah, Nevada, California and Arizona.

Literature Cited

Afanasiev, Michel. 1944. A study of dormancy and germination
of seeds of Cercis canadensis. Journal of
Agricultural Research 69:405-420.